I rig it just like a smelt but with half the leader lenght. I use a 4/0 hook stuck through the base of the head. Stick the point back through the lips and expose the hook on the top of the head. I then half hitch it up and make my last half hitch tight on the tail to prevent spinning.
I use a bait threader and have the hook point sticking out of the mouth with the leader coming ou the anus I have room for about 3 half-hitches at the top. Like TB said make the last one tight. Then I like to wrap the bait with Ghost Cocoon stretchy thread this helps keep the bait flat and helps keep it on the hook/leader. I like using the GC brand because it is clear and can be secured without any half-hitches. Wrapping the bait also helps to when the sculpins are trying to steal your bait. Lastly it really hepls to use fresh anchovies in the estuary.